Witnesses at a high-profile congressional hearing on Islamic radicalization said Thursday that America is "failing" to confront the threat posed by homegrown extremism, as lawmakers for hours traded accusations over whether the inquiry unfairly singled out Muslims.

The hearing, one of the most controversial in recent memory, featured congressmen, a California sheriff, a Muslim scholar and witnesses whose relatives had been recruited by radicals. The afternoon was punctuated by a series of tense moments -- one lawmaker challenged the credibility of the panel, several suggested the committee's time could be better spent looking at groups ranging from the KKK to criminal gangs, and Rep. Peter King, R-N.Y., called a press conference afterward in which he accused the hearing's critics of spreading "mindless hysteria."

King, chairman of the House Homeland Security Committee, also vowed to press ahead with more hearings, telling reporters late Thursday that the next panel would probably focus on Islamic radicalization in the U.S. prison system.

The hearing itself aired a divergent set of views on the scope of the threat posed by radical Islam in the United States and the pertinence of holding a hearing focused solely on that topic.

Zuhdi Jasser, president of the American Islamic Forum for Democracy, said "paralysis" over the issue has seized the nation's leaders and he urged the Muslim community to confront what he called an "exponential increase" in the number of Muslim radicals in the United States.

"The U.S. has a significant problem with Muslim radicalization," said Jasser, who is Muslim. "It is a problem that we can only solve."

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One lawmaker, Rep. Keith Ellison, D-Minn., who is Muslim, cried at the end of his testimony as he described the actions of a Muslim-American paramedic who lost his life in the Sept. 11, 2001, terror attacks. Ellison warned that King was implicating the broader Muslim community with his approach.

King, though, launched the hearing with a robust defense of his decision to press forward. He cited recent terror plots against the United States and suggested the hearings could help fulfill the committee's duty to "protect America from a terrorist attack" by examining the root of recent plots.

"This committee cannot live in denial," King said, accusing critics of trying to "dilute" the focus by turning attention to groups other than Al Qaeda.

"Only Al Qaeda and its Islamist affiliates in this country are part of an international threat to our nation," King said.

He said the hearings "must go forward, and they will." He said backing down would amount to a "craven surrender to political correctness."

But Ellison warned that the hearings could unfairly increase suspicion of Muslim Americans by lumping them together with violent extremists.

"When you assign their violent action to the entire community, you assign collective blame to a whole group," Ellison said. "This is the very heart of stereotyping and scapegoating."

Rep. Bennie Thompson, D-Miss., ranking Democrat on the committee, warned that extremists could exploit the hearing and use it as "propaganda" to inspire a "new generation of suicide bombers."

Lawmakers heard Thursday from two witnesses whose family members were lured away from their community by Islamic radicals.

Melvin Bledsoe, whose son allegedly attacked an Army recruiting center in Arkansas, said Americans are ignoring the issue. He described how his son, Carlos, was radicalized when he went off to college in Nashville, Tenn. He described how his son's personality changed and how, when he returned home for the holidays in 2005, he told his family he converted to Islam. Bledsoe also said he noticed something was wrong when his son took a picture of Martin Luther King Jr. down.

From that point, Carlos changed his name and eventually traveled to Yemen.

"Some Muslim leaders had taken advantage of my son. But he's not the only one being taken advantage of. This is an ongoing thing in Nashville and many other cities in America," Bledsoe said.

King has had around-the-clock security as he pushes forward with the hearings. The New York Republican had extra security Thursday from Capitol Police who are securing the congressional hearing room and surrounding areas, as well as his office.

That's on top of a larger security detail provided by the New York Police Department and the Nassau County, N.Y., police, who have been guarding King for the past few months.

But a new Gallup poll shows that 52 percent of Americans say these hearings are appropriate, though support is split along party lines.

Sixty-nine percent of Republicans say the hearings are the right thing, while only 40 percent of Democrats say they are appropriate. Independents' views track closely to the national average at 51 percent supporting the hearings. Overall, 49 percent of Democrats polled on Tuesday say the hearings are not appropriate, compared to 42 percent of independents and 23 percent of Republicans.

Though Thursday's congressional hearing attracted a high degree of controversy, it's not the first of its kind. Through the years, former Rep. Jane Harman, D-Calif., held four hearings on extremism while serving as an intelligence subcommittee chairwoman; and Sen. Joe Lieberman, D-Conn., held several more as head of the Senate Homeland Security and Government Affairs Committee. King's hearings have been labeled McCarthy-like for targeting Muslims specifically.

In his opening statement, King said he is "well aware" that the hearings have generated "considerable controversy and opposition," but he's not talking about anything different than the Obama administration is considering. He said the congressional inquiry is the "logical response" to the warnings coming out of the Obama administration.

The Obama administration has tried to frame the discussion around radicalization in general, without singling out Muslims. King has said that's just political correctness since Al Qaeda is the main threat to the U.S.